JPH0365382A - Thermosensitive recording material - Google Patents

Abstract

PURPOSE:To enhance thermal response and developed color density, in a thermosensitive recording material containing a usually colorless-light-colored dye precursor and an electron acceptive compound (coupler) forming a color through the reaction with the dye precursor at the time of heating, by containing a specific compound. CONSTITUTION:In a thermosensitive recording material containing a usually colorless-light-colored dye precursor and an electron acceptive compound forming a color through the reaction with the dye precursor at the time of heating, a compound represented by general formula is contained. By this method, the thermosensitive recording material excellent in thermal response and having high color forming sensitivity can be obtained. In the formula, X is a substituted or non-substituted 2C or more alkylene group, an alkenylene group or an alkynylene group, R is a hydrogen atom, a lower alkyl group or a lower alkoxy group and a naphthalene ring may be substituted with a lower alkyl group.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a heat-sensitive recording material, and particularly to a heat-sensitive recording material with excellent thermal responsiveness.

<Prior art> Heat-sensitive recording materials generally have a heat-sensitive recording layer on a support, the main components of which are an electron-donating, usually colorless or light-colored dye precursor and an electron-accepting color developer. , by heating with a thermal pen, laser light, etc., a dye precursor and a color developer react instantaneously to obtain a recorded image, and is disclosed in Japanese Patent Publication No. 43-4160 and Japanese Patent Publication No. 45-14039. etc. are disclosed. These heat-sensitive recording materials have the advantages of being able to record with relatively simple equipment, being easy to maintain, and producing no noise. ,
It is used in a wide range of fields, including ticket vending machines. Particularly in the field of facsimile, the demand for heat-sensitive methods is increasing significantly, and along with this, efforts are being made to increase speed, miniaturize devices, and lower prices in order to reduce transmission costs. As a result, the amount of energy applied for image printing has been steadily decreasing in recent devices. Therefore, there has been a strong demand for the development of highly sensitive heat-sensitive recording materials with high thermal responsiveness that can cope with such higher speed and lower energy facsimiles. In high-speed recording, it is necessary to use the small amount of thermal energy released from the thermal head in an extremely short period of time (usually less than 1 millisecond) for the color reaction to form a high-density color image. be.

As a means to achieve the above objective, it is proposed to use a thermofusible substance with a relatively low melting point as a color development accelerator or sensitizer together with a dye precursor and an electron-accepting compound that causes the dye precursor to develop color. has been done. For example, JP-A-57
-64593, JP-A No. 58-87094 disclose naphthoic acid derivatives;
JP-A-58-110289, JP-A-59-15393
The patent publication discloses naphthoic acid derivatives in JP-A-58-7249.
No. 9, JP-A No. 58-87088 discloses ether and ester derivatives of phenol compounds, and JP-A No. 60-1
No. 10486 proposes the use of parabenzylbiphenyl, JP-A No. 63-130382 proposes the use of 1,1-diphenylethanes, and JP-A No. 63-236678 proposes the use of stilbenes.

However, the heat-sensitive recording materials produced using these methods are still insufficient in terms of thermal response, color development sensitivity, etc.

<Objective of the Invention> An object of the present invention is to obtain a heat-sensitive recording material having excellent thermal responsiveness and high color development sensitivity.

<Structure of the Invention> A heat-sensitive recording material containing a normally colorless or light-colored dye precursor and an electron-accepting compound (color developer) that reacts with the dye precursor upon heating to develop a color, is represented by the following general formula. By containing the compound, it was possible to obtain a heat-sensitive recording material with excellent thermal responsiveness and high color density.

General formula % Formula % (2) (However, in the above formula, X represents a substituted or unsubstituted alkylene group, alkenylene group, or alkynylene group having 2 or more carbon atoms, and R represents a hydrogen atom, a lower alkyl group, or a lower alkoxy group. (In addition, the naphthalene ring in the above formula may be substituted with a lower alkyl group.) Among the general formulas above, those in which X is alkylene have particularly preferable coloring sensitivity.

Specific examples of the compounds of the present invention include those listed in the following formula, but the present invention is not limited thereto.

Compound (1) Compound (3) Compound (4) Compound (5) Compound (9) Compound (8) In addition, for use in heat-sensitive recording materials, the melting point must be 60°C to 160°C.
℃ range is practically preferable.

Note that the compound of the present invention can be easily synthesized by a known method, and can also be easily purified.

Furthermore, among the above compounds, compound (2) and compound (3)
In the case of compound (4), it is convenient to obtain it by condensation of a phosphorus compound and an aldehyde.

The reaction formula is shown below, taking Compound (2) as an example.

(Reaction 1) □ (Reaction 2) 11111) H3 Compound (2) The conditions for reaction 1 are to proceed by heating the raw materials to reflux conditions under a nitrogen atmosphere. Triethyl phosphite as a raw material is used 1.5 times (molar ratio) to 2-bromomethylnaphthalene, and after the reaction is completed, it is distilled off. No particular purification of the product is necessary.

Reaction 2 proceeds on addition of sodium ethylate in DMF solvent. At this time, it is better to cool the reaction mixture with water. After the reaction is completed, the reaction mixture is poured into a large amount of water, and the target product is precipitated. This is washed with water, dried, and recrystallized to obtain a pure product.

As a precaution, the melting points of compounds (2), (3), and (4) are shown.

Compound (2) 89.6-91.0°C Compound (3)
87.1-88.6°C Compound (4) 93.8-9
5.4°C Next, a specific method for producing the heat-sensitive recording material according to the present invention will be described.

The heat-sensitive recording material according to the present invention generally has a heat-sensitive recording layer mainly composed of an electron-donating, usually colorless or light-colored dye precursor and an electron-accepting compound on a support, and can be used with a heat head, a heat pen, or a laser beam. By heating the dye precursor with an electron-accepting compound, a recorded image is obtained by instantaneous reaction between the dye precursor and the electron-accepting compound.
It is disclosed in Publication No. 39 and the like. Further, pigments, sensitizers, antioxidants, anti-sticking agents and the like are added to the heat-sensitive recording layer as necessary.

The dye precursor used in the heat-sensitive recording material according to the present invention is not particularly limited as long as it is generally used in pressure-sensitive recording paper or heat-sensitive recording paper. Specific examples include (1) triarylmethane compounds 3.3-bis(p-dimethylaminophenyl)-6-dimethylaminophthalide (crystal violet lactone), 3.3-bis(p-dimethylamino phenyl)phthalide, 3-(p-dimethylaminophenyl)
-3-(1,2-dimethylindol-3-yl)phthalide, 3-(p-dimethylaminophenyl)-3-(2
-methylindol-3-yl)phthalide, 3-(p
-dimethylaminophenyl)-3-(2-phenylindol-3-yl)phthalide, 3,3-bis(1,2-
dimethylindol-3-yl)-5-dimethylaminophthalide, 3,3-bis(1゜2-dimethylindol-3-yl)-6-dimethylaminophthalide,
3,3-bis(9-ethylcarbazol-3-yl)-
5-dimethylaminophthalide, 3,3-bis(2-phenylindol-3-yl)-5-dimethylaminophthalide, 3-p-dimethylaminophenyl-3-(
1-methylpyrrol-2-yl)-6-dimethylaminophthalide and the like.

(2) Diphenylmethane compounds 4.4'-bis(dimethylaminophenyl)benzhydrylbenzyl ether, N-halophenylleucoauramine, N-2,4,5-trichlorophenylleucoauramine, etc.

(3) Xanthine compound Rhodamine B anilinolactam, Rhodamine B-p-
Chloroanilinolactam, 3-diethylamino-7-
Cybenzylaminofluorane, 3-diethylamino-7
-Octylaminofluorane, 3-diethylamino-
7-phenylfluorane, 3-diethylamino-7-
Chlorofluorane, 3-diethylamino-6-chloro-7-methylfluorane, 3-diethylamino-7
-(3,4-dichloroanilino)fluoran, 3-diethylamino-7-(2-chloroanilino)fluoran,
3-diethylamino-6-methyl-7-anilinofluorane, 3-(N-ethyl-N-tolyl)amino-6
-Methyl-7-anilinofluorane, 3-piperidino-6-methyl-7-anilinofluorane, 3-(N~
ethyl-N-)lyl)amino-6-methyl-7-phenethylfluorane, 3-diethylamino-7-(4nitroanilino)fluorane, 3-dibutylamino-6
-Methyl-7-anilinofluorane, 3-(N-methyl-N-propyl)amino-6-methyl-7-anilinofluorane, 3-(N-ethyl-N-isoamyl)amino-6-methyl -7-anilinofluorane, 3-(N-
Methyl-N-cyclohexyl)amino-6-methyl-7
-anilinofluorane, 3-(N-ethyl-N-tetrahydrofuryl)amino-6-methyl-7-anilinofluorane, etc.

(4) Thiazine compound benzoyl leucomethylene blue, p-nitrobenzoyl leucomethylene blue, etc.

(5) Spiro compounds 3-methylspirodinaphthopyran, 3-ethylspirodinaphthopyran, 3,3°-dichlorospirodinaphthopyran, 3-benzylspirodinaphthopyran, 3-methylnaphtho-(3-methoxybenzo ) spiropyran, 3-propylspilobenzopyran, etc.

These can be used alone or in combination of two or more.

The color developer is not particularly limited as long as it is an acidic substance commonly used in thermal paper. For example, polyvalent metal salts such as phenol derivatives, aromatic carboxylic acid derivatives, N, N'diarylthiourea derivatives, and zinc salts of organic compounds can be used. Particularly preferred are phenol derivatives, such as p-phenylphenol, p-hydroxyacetophenone, 4-hydroxy-4°-methyldiphenylsulfone, 4-hydroxy-4′-isopropoxydiphenylsulfone, and 4-hydroxy-4′-isopropoxydiphenylsulfone. Hydroxy-4°
-benzenesulfonyloxydiphenylsulfone, 1,
1-bis(p-hydroxyphenyl)propane, 1,1
-bis(p-hydroxyphenyl)pentane, 1,1-
Bis(p-hydroxyphenyl)hexane, 1.1-bis(p-hydroxyphenyl)cyclohexane, 2.2
-bis(p-hydroxyphenyl)propane, 2.2-
Bis(p-hydroxyphenyl)hexane, ■.

1-bis(p-hydroxyphenyl)-2-ethylhexane, 2,2-bis(3-chloro-4-hydroxyphenyl)propane, 1,1-bis(p-hydroxyphenyl)-1-phenylethane, 1 .3-G(2-(p-
hydroxyphenyl)-2-propyl]benzene, 1.
3-di[2-(3,4-dihydroxyphenyl)-2
-propyl]benzene, 1,4-di(2-(p-hydroxyphenyl)-2-propyl)benzene, 4.4°
-dihydroxydiphenyl ether, 4.4°-dihydroxydiphenyl sulfone, 3.3°-dichloro-
4,4′-dihydroxydiphenyl sulfone, 3.
3'-Diallyl-4,4°-dihydroxydiphenyl sulfone, 3,3°dichloro-4,4'-dihydroxydiphenyl sulfide, 2,2-bis(4-hydroxyphenyl)acetic acid/methyl, 2,2-bis( 4-hydroxyphenyl)butyl acetate, 4,4°-thiobis(2-
j=nibutyl 5-methylphenol), benzyl p-hydroxybenzoate, chlorobenzyl p-hydroxybenzoate, dimethyl 4-hydroxyphthalate, benzyl gallate, stearyl gallate, salicylanilide, 5-chlorosalicylanilide, etc. .

Binders used in heat-sensitive recording materials include starches, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, gelatin, casein,
Alkali salts of polyvinyl alcohol, modified polyvinyl alcohol, sodium polyacrylate, acrylic amide/acrylic ester copolymer, acrylic amide/acrylic ester/methacrylic acid ternary copolymer, styrene/maleic anhydride copolymer , water-soluble adhesives such as alkali salts of ethylene/maleic anhydride copolymers, polyvinyl acetate, polyurethane, polyacrylic esters, styrene/butadiene copolymers, acrylonitrile/butadiene copolymers, methyl acrylate/butadiene copolymers Examples include polymers and latexes such as ethylene/vinyl acetate copolymers.

In addition, N-
Waxes such as hydroxymethyl stearamide, stearamide, and palmitic acid amide. Naphthol derivatives such as 2-benzyloxynaphthalene. Biphenyl derivatives such as p-benzylbiphenyl and 4-allyloxybiphenyl. 1.2-bis(3-methylphenoxy)
Polyether compounds such as ethane, 2.2'-bis(4-methoxyphenoxy) diethyl ether, and bis(4-methoxyphenyl) ether. Carbonic acid or oxalic acid diester derivatives such as diphenyl carbonate, dibenzyl oxalate, and bis(p-methylbenzyl) oxalate ester can be added in combination.

Examples of the pigment include diatomaceous earth, talc, kaolin, calcined kaolin, calcium carbonate, magnesium carbonate, titanium oxide, zinc oxide, silicon oxide, aluminum hydroxide, urea-formalin resin, and the like.

In addition, higher fatty acid metal salts such as zinc stearate and calcium stearate, waxes such as paraffin, oxidized paraffin, polyethylene, oxidized polyethylene, stearic acid amide, and castor wax are used to prevent head wear and stickiness, as well as dioctyl sulfosuccinate. Dispersants such as sodium chloride, ultraviolet absorbers such as benzophenone and benzotriazole, and surfactants, fluorescent dyes, and the like are added as necessary.

As the support used in the present invention, paper is mainly used, but nonwoven fabric, plastic film, synthetic paper, metal foil, etc., or a composite sheet of a combination of these can also be used as desired. In addition, in the production of heat-sensitive recording materials, an overcoat layer is provided to protect the heat-sensitive recording layer, and an undercoat layer consisting of a single layer or multiple layers of pigment or resin is provided between the heat-sensitive recording layer and the support. Various known techniques can be used.

The amount of coating on the heat-sensitive recording layer is determined by the amount of dye precursor and color developer, which are color forming components, and is usually 0.1 to 1.0 g.
/ml is appropriate.

The color developer is added in an amount of 5 to 400% by weight based on the dye precursor, with a particularly preferable addition amount of 20 to 300% by weight.

In addition, the compound according to the present invention has a content of 5 to 400 with respect to the color developer.
The amount added is preferably 20 to 300% by weight.

<Example> Next, the present invention will be explained in more detail with reference to Examples.

Note that all parts and percentages shown below are based on weight.

(Example 1) Preparation of heat-sensitive recording material (1) Preparation of heat-sensitive coating liquid Dye precursor 3-dibutylamino-6-methyl-7
- 35 parts of anilinofluorane was ground with 80 parts of a 2.5% polyvinyl alcohol aqueous solution in a ball mill for 2.4 hours to obtain a dye dispersion. Next, 40 parts of 2,2-bis(p-hydroxyphenyl)propane and 60 parts of a 2.5% polyvinyl alcohol aqueous solution were ground in a ball mill for 24 hours to obtain a color developer dispersion. Compound (1) 55 parts to 2
．． The mixture was ground with 120 parts of a 5% aqueous polyvinyl alcohol solution in a ball mill for 24 hours to obtain a dispersion of the compound of the present invention.

After mixing the above three types of dispersions, the following were added and mixed well while stirring to prepare a heat-sensitive coating liquid.

50% calcium carbonate dispersion 100 parts 40% zinc stearate dispersion 50 parts 10% polyvinyl alcohol aqueous solution 200 parts water
280 copies (2) Preparation of heat-sensitive coated paper A coating liquid consisting of the following composition is smeared on base paper with a basis weight of 40 g/nf to a solid content of 9 g/rd, dried, and heat-sensitive coated paper is prepared. It was created.

Calcined kaolin 100 parts Styrene-butadiene latex 50% aqueous dispersion 24 parts water
200 copies (3) Preparation of heat-sensitive recording material The heat-sensitive coating liquid prepared in (1) was smeared onto the surface of the heat-sensitive coating paper prepared in (2) so that the solid content was 4 g/rd, and dried. A heat-sensitive recording material was created.

(Example 2) A heat-sensitive recording material was prepared in the same manner as in Example 1 except that compound (1) in Example 1 was changed to compound (2).

(Example 3) A heat-sensitive recording material was prepared in the same manner as in Example 1 except that compound (1) in Example 1 was changed to compound (3).

(Example 4) A heat-sensitive recording material was produced in the same manner as in Example 1 except that compound (1) in Example 1 was changed to compound (4).

(Example 5) Thermal recording was carried out in the same manner as in Example 1, except that a mixture of 13 parts of compound (1) and 42 parts of 2-benzyloxynaphthalene was used instead of 55 parts of compound (1) in Example 1. Created the material.

(Comparative example) Example 1 except that compound (1) in Example 1 was removed.
A heat-sensitive recording material was prepared in the same manner as above.

(Evaluation) The heat-sensitive recording materials obtained in Examples 1 to 5 and Comparative Examples were calendered so that the Bekk smoothness of the heat-sensitive coated surface was about 500 seconds, and then subjected to a facsimile tester T manufactured by Okura Electric Co., Ltd.
A printing test was conducted using H-PMD. Dot density 8
dots/mm, using a thermal head with head resistance of 185Ω, head voltage of 11V, pulse width of 0, 7 and 1.0.
Printing was performed by applying electricity in milliseconds, and the color density was measured using a Macbeth RD-918 reflection densitometer. The results are shown in the table below.

Table <Effects of the Invention> As is clear from the examples, by incorporating the compound according to the present invention, it was possible to obtain a heat-sensitive recording material with excellent thermal response and high color development sensitivity.

Claims (1)

[Scope of Claims] 1. A heat-sensitive recording material containing a normally colorless or light-colored dye precursor and an electron-accepting compound that reacts with the dye precursor upon heating to cause the dye precursor to develop a color, a compound represented by the following general formula: A heat-sensitive recording material characterized by containing. General formula ▲ Numerical formula, chemical formula, table, etc. ▼ (However, in the above formula, X represents a substituted or unsubstituted alkylene group, alkenylene group, or alkynylene group having 2 or more carbon atoms, and R is a hydrogen atom or a lower alkyl group. or represents a lower alkoxy group.Also, the naphthalene ring in the above formula may be substituted with a lower alkyl group.)